Democratic presidential candidate Kamala Harris said Wednesday that she disagrees with rival Joe Biden's argument that the 1994 crime bill didn't lead to mass incarcerations of black people.

"That 1994 crime bill, it did contribute to mass incarceration in our country. It encouraged and was the first time that we had a federal three strikes law," Harris, a senator from California, said while campaigning in New Hampshire. "It funded the building of more prisons in the states. So I disagree, sadly."

Biden, then a senator from Delaware, helped write the legislation, which was seen at the time as a tool to crack down on crime but has since been derided as needlessly leading to the jailing of a generation of people of color. The bill could emerge as a key vulnerability for the former vice president as he works to appeal to both working class white voters and more diverse progressives.

As a former district attorney and California attorney general, Harris has also faced scrutiny among some progressives for her ties to law enforcement.

The former vice president on Wednesday did receive support for the crime bill from an unexpected and perhaps unwelcome source: President Donald Trump's personal lawyer, former New York City Mayor Rudy Giuliani.

"The 1994 Crime Bill passed by Pres. Clinton and Speaker Gingrich, with Biden & Schumer as the leaders in Senate and House, helped me and the NYPD reduce murder from @ 1,900 a year to @ 500 and then under Mayor Bloomberg to @ 350," Giuliani wrote. "That's over 20,000 lives saved. Joe don't cave."

As a presidential candidate, Biden is hoping to be nominated to take on Trump in 2020.

Despite Harris' disagreement with Biden on the crime bill, she warmly welcomed him to the presidential race, which now features 22 Democrats. With Biden emerging as an early front-runner, Harris has faced questions about whether she would be his running mate.

On Wednesday, she turned the issue around.

"If people want to speculate about running mates, I encourage that," Harris said. "Because I think that Joe Biden would be a great running mate. As vice president, he's proven that he knows how to do the job."

In an interview with The Associated Press on Monday, Biden praised the Democratic field but didn't commit to picking a woman as his vice president. At the same time, he didn't rule out taking a position in a future Democratic administration if he doesn't win the nomination in 2020.

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